LiFeP04 Charging Question

[ctva]

I am looking to put two 100ah LiFeP04 batteries in for the house bank to replace the current 3x85ah lead acid batteries, with a 4th 85ah Lead Acid being for the engine which will remain.

Currently the charging is done to the two banks via the 55amp alternator and splitting diode. This will be changed to charge only the enging battery. From this, a Renogy 30amp DC-DC (the one with MPPT to bring in the 200w solar panels output) will charge the LiFeP04 batteries. This is hopefully all pretty straight forward to this point.

The question is, at present I have a Sterling ProCharge Ultra which charges both banks. In the new setup, what would the best way to wire this in be? I can think of several options:

1 - Amend the ProCharge Ultra to LiFeP04 and charge the two LiFeP04 batteries directly.
2 - As the charger would only be used when the engine is not running, put the input to go through the DC-DC charger.
3 - Keep the Pro Charge Ultra at Lead Acid and only charge the engine battery which I assume would then kick in the DC-DC charger to charge the domestic bank.
4 - Or is there another better way that I have not thoght of?

I'm not even sure if all of these is are options or even possible.

Unfortunately I am having difficulty in distilling the online info so any assistance or pointing in the right information resource would be appreciated.

 

[mattonthesea]

Very similar to you. I use option 3. There is a little inefficiency this way but it means the engine battery is priority

 

[fredrussell]

Does the ProCharge Ultra have a LiFePo setting?

 

[Krumelur]

I'm using option 3. The old charger goes to the lead-acid battery. The DC-DC charger connects the LiFePo4s if there's enough voltage on the starter battery, wherever it's coming from.
My solar charger is connected to the LiFePo4s directly.
I'm using Victron DC-DC and Solar equipment.

 

[ctva]

Does the ProCharge Ultra have a LiFePo setting?

Yes, as far as I know.

 

[geem]

Does the ProCharge Ultra have a LiFePo setting?

There is a custom setting for voltage. Not sure you can adjust absorbtion time though. The option would be to set the charge voltage down to about 3.4v per cell ( 13.6v) then you are not going to cause any problems.

 

[geem]

I am looking to put two 100ah LiFeP04 batteries in for the house bank to replace the current 3x85ah lead acid batteries, with a 4th 85ah Lead Acid being for the engine which will remain.

Currently the charging is done to the two banks via the 55amp alternator and splitting diode. This will be changed to charge only the enging battery. From this, a Renogy 30amp DC-DC (the one with MPPT to bring in the 200w solar panels output) will charge the LiFeP04 batteries. This is hopefully all pretty straight forward to this point.

The question is, at present I have a Sterling ProCharge Ultra which charges both banks. In the new setup, what would the best way to wire this in be? I can think of several options:

1 - Amend the ProCharge Ultra to LiFeP04 and charge the two LiFeP04 batteries directly.
2 - As the charger would only be used when the engine is not running, put the input to go through the DC-DC charger.
3 - Keep the Pro Charge Ultra at Lead Acid and only charge the engine battery which I assume would then kick in the DC-DC charger to charge the domestic bank.
4 - Or is there another better way that I have not thoght of?

I'm not even sure if all of these is are options or even possible.

Unfortunately I am having difficulty in distilling the online info so any assistance or pointing in the right information resource would be appreciated.

I would charge the lead battery only with the Pro charge Ultra. That way you get both banks charged. Once everything is charged, both batteries will go to float.

 

[ctva]

Thanks one and all for the time taken to respond. I had also come to the conclusion that option 3 was the simplest but as usual, over thinking tends to make you question your answer.

Thanks

Chris

 

[Neeves]

A conclusion I draw, but think of it as a question.

If you run your 200amp of LiFePo4 down (the ability to do so is one of the advantages of Lithium) then its going to take you a devil of a time to recharge the Lithiums.

Jonathan

 

[geem]

A conclusion I draw, but think of it as a question.

If you run your 200amp of LiFePo4 down (the ability to do so is one of the advantages of Lithium) then its going to take you a devil of a time to recharge the Lithiums.

Jonathan

The OP is installing a very small amount of lithium to replace 3x85Ah domestic batteries. 200w of solar. It would be reasonable to assume he doesnt have large loads. Yes, it would take a while to recharge, if he made full use of the capacity, but the reality is he doesn't need to fully recharge. The beauty of lithium. They will come to no harm being sat at 20%. If the boat is left on a mooring with no load or in a marina, the lithium will charge up with solar in a few days.

 

[ctva]

@Neeves , thanks for the question. @geem has kind of summed it up. I do not envisage ever running the lithiums right down (touching all wood available), but accept the inefficiency of charging this way when on mains power which we only use when visiting the boat in the winter to be honest. The rest of the time it's just solar and alternator when motoring.

 

[Daverw]

I’m in the same process of removing argofet and fitting dc dc charger to be ready for house bank change next year, planning on alternator charging via starter battery with multipus connected as currently charging house with trickle charge to starter when on shore power and all solar direct to house bank, currently 450Ah agm

 

[NBs]

I recommend getting a lifepo4 charger, I have this one and it's proven to be a good one. Check the bsm charge value of your batteries and if your batteries are connected in parallel, the bsm can be loaded twice vs one battery.

Amazon.com

 

[geem]

I recommend getting a lifepo4 charger, I have this one and it's proven to be a good one. Check the bsm charge value of your batteries and if your batteries are connected in parallel, the bsm can be loaded twice vs one battery.

Amazon.com

The charge voltage of that charger is way too high in my opinion. At 3.65v/cell you are on the absolute maximum limit for what is safe. There in no need to charge above 14v. Anything higher and you stress the batteries for a tiny increase in battery charge capacity, circa less than 3%. I would not use that charger on my lithium batteries

 

[Daverw]

I’ve found that planning the upgrade over time and making sure all charging sources have good lipofe4 profiles with adjustments as needed has made the planned change easier, I’ve gone all Victron anyway

 

[lustyd]

@Neeves , thanks for the question. @geem has kind of summed it up. I do not envisage ever running the lithiums right down (touching all wood available), but accept the inefficiency of charging this way when on mains power which we only use when visiting the boat in the winter to be honest. The rest of the time it's just solar and alternator when motoring.

Look at it the other way, your lithium will always have at least as many Ah as the old lead but with way more headroom for charge. It would be a shame to have a sunny day and nowhere to store that free charge. Lithium needs a very different mindset, ours is usually between 60-80% but occasionally hits 99% when we’re away for a week or two and it’s sunny. I might consider fully charging before a big trip but otherwise don’t generally.

 

[NBs]

The charge voltage of that charger is way too high in my opinion. At 3.65v/cell you are on the absolute maximum limit for what is safe. There in no need to charge above 14v. Anything higher and you stress the batteries for a tiny increase in battery charge capacity, circa less than 3%. I would not use that charger on my lithium batteries

As far as I know, 14V is not enough to start the balancing between the cells and so the battery will sooner or later get into a state where the V of the different cells are too spread out and the capacity of the battery will be lost. Batteries should be balanced every 2-3 months and parallel connected batteries should be charged to full 14.6V individually or another option is to buy a separate balancer. I agree that the voltage can stay normal even at 13.6 if you have enough A in the bank, but between you need to go from 14.4-14.6V to achieve cell balance.

I also think that the 4 cells of the battery are hardly ever in perfect balance, so the charger/bsm will cut off when one of the cells is at 14,6V and also you can at any time stop the charger itself, from the charger, you can see what A it has charged if you don't have a battery monitor. I also have a previous victron phoneix charger which I use in conjunction with a lifepower charger when I want a quick charge from a dock or auxiliary engine AC 230V per hour at about 100A, but I monitor the charge, not charge the batteries to full. I also have a 50A dc-dc charger with the parameters set softer, so the battery doesn't suffer for a long day.

 

[geem]

As far as I know, 14V is not enough to start the balancing between the cells and so the battery will sooner or later get into a state where the V of the different cells are too spread out and the capacity of the battery will be lost. Batteries should be balanced every 2-3 months and parallel connected batteries should be charged to full 14.6V individually or another option is to buy a separate balancer. I agree that the voltage can stay normal even at 13.6 if you have enough A in the bank, but between you need to go from 14.4-14.6V to achieve cell balance.

It depends on your batteries. A good lithium battery with Bluetooth and active balancer can be set up to suit. We start balancing at 3.45v per cell. We charge to 3.5v per cell. The battery is in absorption for 15mins. With a 2A active balancer, 15 mins is plenty as quite often we need no balancing at all. The last full charge for our batteries was 22 days ago. Our lithium batteries use grade A cells and behave impeccably. The batteries see large loads from using a 220v watermaker, electric cooking, etc, via a 3kw inverter. Even with these high loads, that often induce cell imbalance, we don't see more than 5mV difference when charging near the 3.5v/cell mark.
If you have a battery from the cheap end of the market, I honestly believe that the manufacturers don't install Bluetooth so that you cannot see what is happening at cell level. They give you no ability to see or change settings. This is to their advantage not yours. They can sell you poor quality, mismatched cells and you will be none the wiser until you have a BMS shutdown. I have been advised that the cost of fitting Bluetooth would be as low as £2.
If you have such a battery, you may need to spend a long time in float for the passive balancer to get the cell balance under control. This can only be done at high voltages on such a battery. This will likely lead to reduce battery life.
It is worth noting that a widening voltage between each cell doesn't reduce the capacity of the battery. The implications is more likely to be a BMS shutdown as the highest cell hits the upper safely limit for voltage. When this happens, you don't want to be navigating in the dark, entering a harbour in the rain and wind with no chartplotter, depth sounder, vhf, etc
I would encourage anybody choosing to go lithium to post on this forum about their intended battery choice. There are several knowledgeable formites that can assist in the purchase and explain the pitfalls

 

[yoda]

a. I would take option 1 and fit a second small charger for the engine start battery.
b. Why fit 2 x 100Ah batteries and not 1 x 200 Ah battery. The challenge of making the 2 batteries share load and charging evenly is removed and make wiring simpler.
c. A good battery monitor like the Victron BMV 702 gives you a really good indication of state of charge and is well worth the money.

 

[Daverw]

Just seen on off grid garage Andy has the latest EVE 304Ah cells,the price also seems to be dropping, looks like 8 off these may have to be purchased soon, need to decide which bms to use that will talk to victron network